To conduct a drill stem test of an earth formation interval that has been intersected by a well bore, a packer and a normally closed test valve are lowered into the well on a pipe string, and the packer is set to isolate the formation interval to be tested. The test valve then is opened and closed for flow and shut-in periods of time, during which changes in the pressure of fluids in the well bore below the test valve are recorded by a gauge. The pressure data thus obtained may be analyzed when the test tool string is removed from the well, or while the test is in progress using known equipment and systems which enable a surface readout of the data.
Pressure data taken from various locations within the tool string and in the well bore are of interest from several standpoints. Of course measurements of the changes in pressure that occur below the test valve during the shut-in period of the test provide the basis for determining highly useful characteristics of the formation such as permeability and initial reservoir pressure. A knowledge of pressures below the test valve also enables the operator to monitor whether the test is proceeding properly and if the equipment is functioning in its intended manner. Various malfunctions such as tool plugging can be detected, and the respective durations of the flow and shut-in periods can be optimized. It also is very useful to know the pressure changes that are occurring inside the tool string above the test valve. From these pressures knowledge can be gained as to the amount and type of fluid recovery, as well as some of its characteristics such as density and specific gravity. Pressures above the test valve provide an indication of the operation of other valve systems in the tool string such as the operation of a reversing valve that is responsive to repeated applications of pressure to the interior of the pipe string. It also is desirable to monitor the pressure of fluids standing in the well annulus above the packer in order to determine that correct operating pressures are being applied to the fluids to cause actuation of the main test valve, as well as annulus pressure controlled sampler valves and circulating valves that may be included in the combination of tools being used. Leaks associated with the packer or the pipe string also may be detected by monitoring the pressure of fluids in the well annulus.
Prior drill stem testing equipment that applicant is aware of has not had the capability for making multiple pressure measurements of the type described above, and therefore has provided the tool operator at the surface with limited information as to the progress of the test and the operation of the equipment downhole.
It is accordingly a general object of the present invention to provide a new and improved full bore drill stem testing apparatus that includes a plurality of pressure transducers and separate porting arrangements to enable the measurement and recording of the pressures of well fluids in the tool string below and above the test valve as well as in the annulus adjacent the tool string.
Another object of the present invention is to provide a drill stem testing apparatus of the type described that includes separate ports for sensing the pressure of fluids above and below the main test valve and in the annulus adjacent the tool string, and means for communicating a selected one of the ports with a pressure transducer means.
Another object of the present invention is to provide a new and improved full bore drill stem testing apparatus having a multiple porting system for monitoring the pressures of fluids below and above the test valve as well as in the annulus adjacent the tool string, the porting system including plug components that are interchangeable in a manner such that different ports can be employed to sense selected ones of the pressures of interest.